Include trailing comma in multiline Debug representation #59076

dtolnay · 2019-03-10T21:34:27Z

This PR changes the behavior of Formatter::debug_struct, debug_tuple, debug_list, debug_set, and debug_map to render trailing commas in {:#?} mode, which is the dominant style in modern Rust code.

Before:

Language {
    name: "Rust",
    trailing_commas: false
}

After:

Language {
    name: "Rust",
    trailing_commas: true,
}

rust-highfive · 2019-03-10T21:34:31Z

r? @kennytm

(rust_highfive has picked a reviewer for you, use r? to override)

Mark-Simulacrum · 2019-03-11T03:06:24Z

Is there any reason to do this, beyond being nicer from a formatting perspective?

@rustbot modify labels to relnotes.

dtolnay · 2019-03-11T03:21:21Z

I would say that's the only reason. I won't try to argue that this makes debugging easier. 😉

The current behavior of DebugStruct was designed before the code style for Rust had been as well established. You can see in RFC 640 which proposed {:#?} there is this code fragment under Motivation without a trailing comma:

pub struct BufferedStream<S> {
    inner: BufferedReader<InternalBufferedWriter<S>>
}

I believe if the feature were being implemented from scratch today it would certainly be done with a trailing comma. This PR only closes the gap between the way it was built in 2015 and the way we would build it today.

petrochenkov · 2019-03-11T07:02:30Z

Is there any reason to do this, beyond being nicer from a formatting perspective?

Code in libcore/fmt is simpler, for example.
Being friendly to code generators is one of the primary reasons why trailing separators are supported in general.

Mark-Simulacrum · 2019-03-11T16:46:24Z

I will make the note that this is likely to cause somewhat widespread test breakage in the community; I don't think that's a reason to not do this, but worth noting. We can run crater if we want to know ahead of time.

@bors try in case we decide to go ahead with a crater run

I presume we'll want an FCP for libs team? Let's try r? @Amanieu for the review

bors · 2019-03-11T16:46:42Z

⌛ Trying commit ddcfe2b5d359b9a4b925f037a1874a0a4fcdc801 with merge 0f4bc26daf93fffc14b0a6557b12eab1844ecfda...

bors · 2019-03-11T19:05:03Z

☀️ Try build successful - checks-travis
Build commit: 0f4bc26daf93fffc14b0a6557b12eab1844ecfda

Dylan-DPC-zz · 2019-03-18T21:56:07Z

ping from triage @Amanieu / @rust-lang/libs any updates?

alexcrichton · 2019-03-18T22:16:10Z

I would personally think that we can land this at any time (and should) but @Mark-Simulacrum do you feel that this definitely needs a crater run? I think I probably expect less breakage than you though

Mark-Simulacrum · 2019-03-19T02:42:07Z

Not at all; I expect breakage but probably just local (i.e., tests) and we're generally pretty free to break those. We'll (someone from the release team) probably just open an issue once next beta is cut with this in it and we get a crater run on that, we can assess breakage then. Seems fine to land for now though!

@bors r=alexcrichton (I also glanced through but tests and nothing seems obviously bad)

bors · 2019-03-19T02:42:09Z

📌 Commit ddcfe2b5d359b9a4b925f037a1874a0a4fcdc801 has been approved by alexcrichton

bors · 2019-03-19T18:07:59Z

☔ The latest upstream changes (presumably #59293) made this pull request unmergeable. Please resolve the merge conflicts.

KamilaBorowska · 2019-03-20T16:54:53Z

Well, it is a breaking change, and I saw code (although not in Rust) that parsed formatting output in order to get information that is otherwise unobtainable. However, while I can believe some Rust programmers did that, I would assume most were reasonable enough to use {:?} instead of {:#?} to avoid unnecessary whitespace.

Centril · 2019-03-30T13:12:10Z

Ping from triage, @dtolnay, you have some rebasing todo.

dtolnay · 2019-04-03T14:37:08Z

Rebased to fix conflict with #57847 in src/test/ui/rfc-2361-dbg-macro/dbg-macro-expected-behavior.rs.
Passed ./x.py test locally.

@bors r=alexcrichton

Accept trailing comma in test of impl Debug for PackageId The standard library is planning to begin emitting trailing commas in multiline Debug representations to align with the dominant style in modern Rust code -- rust-lang/rust#59076. ```diff PackageId { name: "foo", version: "1.0.0", - source: "registry `https://github.com/rust-lang/crates.io-index`" + source: "registry `https://github.com/rust-lang/crates.io-index`", } ``` For now, change this tests to accept both with and without trailing comma. Once the trailing comma change reaches the stable channel we will be able to remove one of the cases.

dtolnay · 2019-04-04T17:38:38Z

Working on it -- I submitted rust-lang/cargo#6818 to fix the test case in Cargo, currently waiting on the Cargo update in rust-lang/rust: #59681.

@ehuss

Update cargo 20 commits in 63231f438a2b5b84ccf319a5de22343ee0316323..6f3e9c367abb497c64f360c3839dab5e74928d5c 2019-03-27 12:26:45 +0000 to 2019-04-04 14:11:33 +0000 - Fix Init for Fossil SCM project (rust-lang/cargo#6792) - Fix member_manifest_version_error accessing the network (rust-lang/cargo#6799) - Don't include email if it is empty (rust-lang/cargo#6802) - Fix unused import warning (rust-lang/cargo#6807) - Add some help and documentation for unstable flags (rust-lang/cargo#6791) - Allow `cargo doc --open` with multiple packages (rust-lang/cargo#6803) - Allow `cargo install --path P` to load config from P (rust-lang/cargo#6804) - Add more suggestions on how to deal with excluding a package from a workspace (rust-lang/cargo#6805) - Warn on version req with metadata (rust-lang/cargo#6806) - cargo install: Be more restrictive about cli flags (rust-lang/cargo#6801) - Support force-pushed repos with git-fetch-with-cli (rust-lang/cargo#6800) - Cargo clippy (rust-lang/cargo#6759) - Don't include metadata in wasm binary examples (rust-lang/cargo#6812) - Update glossary for `feature` (rust-lang/cargo#6809) - Include proc-macros in `build-override` (rust-lang/cargo#6811) - Resolver: A dep is equivalent to one of the things it can resolve to (rust-lang/cargo#6776) - Add some docs for `Downloads` (rust-lang/cargo#6815) - Resolve: Be less strict while offline (rust-lang/cargo#6814) - Accept trailing comma in test of impl Debug for PackageId (rust-lang/cargo#6818) - Fix doc link (rust-lang/cargo#6820) <br> I specifically care about "Accept trailing comma in test of impl Debug for PackageId (rust-lang/cargo#6818)" to unblock rust-lang#59076. Mentioning @ehuss.

@ehuss

Update cargo 20 commits in 63231f438a2b5b84ccf319a5de22343ee0316323..6f3e9c367abb497c64f360c3839dab5e74928d5c 2019-03-27 12:26:45 +0000 to 2019-04-04 14:11:33 +0000 - Fix Init for Fossil SCM project (rust-lang/cargo#6792) - Fix member_manifest_version_error accessing the network (rust-lang/cargo#6799) - Don't include email if it is empty (rust-lang/cargo#6802) - Fix unused import warning (rust-lang/cargo#6807) - Add some help and documentation for unstable flags (rust-lang/cargo#6791) - Allow `cargo doc --open` with multiple packages (rust-lang/cargo#6803) - Allow `cargo install --path P` to load config from P (rust-lang/cargo#6804) - Add more suggestions on how to deal with excluding a package from a workspace (rust-lang/cargo#6805) - Warn on version req with metadata (rust-lang/cargo#6806) - cargo install: Be more restrictive about cli flags (rust-lang/cargo#6801) - Support force-pushed repos with git-fetch-with-cli (rust-lang/cargo#6800) - Cargo clippy (rust-lang/cargo#6759) - Don't include metadata in wasm binary examples (rust-lang/cargo#6812) - Update glossary for `feature` (rust-lang/cargo#6809) - Include proc-macros in `build-override` (rust-lang/cargo#6811) - Resolver: A dep is equivalent to one of the things it can resolve to (rust-lang/cargo#6776) - Add some docs for `Downloads` (rust-lang/cargo#6815) - Resolve: Be less strict while offline (rust-lang/cargo#6814) - Accept trailing comma in test of impl Debug for PackageId (rust-lang/cargo#6818) - Fix doc link (rust-lang/cargo#6820) <br> I specifically care about "Accept trailing comma in test of impl Debug for PackageId (rust-lang/cargo#6818)" to unblock #59076. Mentioning @ehuss.

This commit changes the behavior of Formatter::debug_struct, debug_tuple, debug_list, debug_set, and debug_map to render trailing commas in {:#?} mode, which is the dominant style in modern Rust code. Before: Language { name: "Rust", trailing_commas: false } After: Language { name: "Rust", trailing_commas: true, }

dtolnay · 2019-04-05T13:49:35Z

Rebased on #59681 and tested again with ./x.py test. Is there a more exhaustive test command that I could run locally that would run the test suites of whichever tools are tested in Travis?

@bors r=alexcrichton

bors · 2019-04-05T13:49:36Z

📌 Commit cfd31fb has been approved by alexcrichton

bors · 2019-04-05T15:01:14Z

⌛ Testing commit cfd31fb with merge 20dbf28...

Include trailing comma in multiline Debug representation This PR changes the behavior of [`Formatter::debug_struct`](https://doc.rust-lang.org/std/fmt/struct.Formatter.html#method.debug_struct), [`debug_tuple`](https://doc.rust-lang.org/std/fmt/struct.Formatter.html#method.debug_tuple), [`debug_list`](https://doc.rust-lang.org/std/fmt/struct.Formatter.html#method.debug_list), [`debug_set`](https://doc.rust-lang.org/std/fmt/struct.Formatter.html#method.debug_set), and [`debug_map`](https://doc.rust-lang.org/std/fmt/struct.Formatter.html#method.debug_map) to render trailing commas in `{:#?}` mode, which is the dominant style in modern Rust code. #### Before: ```console Language { name: "Rust", trailing_commas: false } ``` #### After: ```console Language { name: "Rust", trailing_commas: true, } ```

bors · 2019-04-05T17:45:36Z

☀️ Test successful - checks-travis, status-appveyor
Approved by: alexcrichton
Pushing 20dbf28 to master...

rust-lang/rust/pull/59076 changed the multiline Debug representation to always include a trailing comma. This change currently breaks our tests on beta and nightly, since we use this Debug representation to compare expected parsing output. We cannot simply add the trailing commas to the expected output strings, since that would break on older rustc versions we support. Instead, this commit makes it so that all trailing commas are stripped before the comparison. This workaround can be removed once rust-lang/rust/pull/59076 reaches our minimum supported rustc version.

* Ignore trailing commas in `ExpectedDebug` rust-lang/rust/pull/59076 changed the multiline Debug representation to always include a trailing comma. This change currently breaks our tests on beta and nightly, since we use this Debug representation to compare expected parsing output. We cannot simply add the trailing commas to the expected output strings, since that would break on older rustc versions we support. Instead, this commit makes it so that all trailing commas are stripped before the comparison. This workaround can be removed once rust-lang/rust/pull/59076 reaches our minimum supported rustc version. * Bump minimum Rust version to 1.31.0 That's required by the current version rustc-demangle, which is a dependency of mdbook.

* Ignore trailing commas in `ExpectedDebug` rust-lang/rust/pull/59076 changed the multiline Debug representation to always include a trailing comma. This change currently breaks our tests on beta and nightly, since we use this Debug representation to compare expected parsing output. We cannot simply add the trailing commas to the expected output strings, since that would break on older rustc versions we support. Instead, this commit makes it so that all trailing commas are stripped before the comparison. This workaround can be removed once rust-lang/rust/pull/59076 reaches our minimum supported rustc version. * Bump minimum Rust version to 1.31.0 That's required by the current version rustc-demangle, which is a dependency of mdbook. * Replace all uses of `try!` with `?` The `?` operator was added to replace the `try!` macro and should be used in modern Rust code. `try` is also a reserved keyword in Rust 2018, so this change prepares for a possible edition switch too.

Version 1.35.0 (2019-05-23) ========================== Language -------- - [`FnOnce`, `FnMut`, and the `Fn` traits are now implemented for `Box<FnOnce>`, `Box<FnMut>`, and `Box<Fn>` respectively.][59500] - [You can now coerce closures into unsafe function pointers.][59580] e.g. ```rust unsafe fn call_unsafe(func: unsafe fn()) { func() } pub fn main() { unsafe { call_unsafe(|| {}); } } ``` Compiler -------- - [Added the `armv6-unknown-freebsd-gnueabihf` and `armv7-unknown-freebsd-gnueabihf` targets.][58080] - [Added the `wasm32-unknown-wasi` target.][59464] Libraries --------- - [`Thread` will now show its ID in `Debug` output.][59460] - [`StdinLock`, `StdoutLock`, and `StderrLock` now implement `AsRawFd`.][59512] - [`alloc::System` now implements `Default`.][59451] - [Expanded `Debug` output (`{:#?}`) for structs now has a trailing comma on the last field.][59076] - [`char::{ToLowercase, ToUppercase}` now implement `ExactSizeIterator`.][58778] - [All `NonZero` numeric types now implement `FromStr`.][58717] - [Removed the `Read` trait bounds on the `BufReader::{get_ref, get_mut, into_inner}` methods.][58423] - [You can now call the `dbg!` macro without any parameters to print the file and line where it is called.][57847] - [In place ASCII case conversions are now up to 4× faster.][59283] e.g. `str::make_ascii_lowercase` - [`hash_map::{OccupiedEntry, VacantEntry}` now implement `Sync` and `Send`.][58369] Stabilized APIs --------------- - [`f32::copysign`] - [`f64::copysign`] - [`RefCell::replace_with`] - [`RefCell::map_split`] - [`ptr::hash`] - [`Range::contains`] - [`RangeFrom::contains`] - [`RangeTo::contains`] - [`RangeInclusive::contains`] - [`RangeToInclusive::contains`] - [`Option::copied`] Cargo ----- - [You can now set `cargo:rustc-cdylib-link-arg` at build time to pass custom linker arguments when building a `cdylib`.][cargo/6298] Its usage is highly platform specific. Misc ---- - [The Rust toolchain is now available natively for musl based distros.][58575] [59460]: rust-lang/rust#59460 [59464]: rust-lang/rust#59464 [59500]: rust-lang/rust#59500 [59512]: rust-lang/rust#59512 [59580]: rust-lang/rust#59580 [59283]: rust-lang/rust#59283 [59451]: rust-lang/rust#59451 [59076]: rust-lang/rust#59076 [58778]: rust-lang/rust#58778 [58717]: rust-lang/rust#58717 [58369]: rust-lang/rust#58369 [58423]: rust-lang/rust#58423 [58080]: rust-lang/rust#58080 [57847]: rust-lang/rust#57847 [58575]: rust-lang/rust#58575 [cargo/6298]: rust-lang/cargo#6298 [`f32::copysign`]: https://doc.rust-lang.org/stable/std/primitive.f32.html#method.copysign [`f64::copysign`]: https://doc.rust-lang.org/stable/std/primitive.f64.html#method.copysign [`RefCell::replace_with`]: https://doc.rust-lang.org/stable/std/cell/struct.RefCell.html#method.replace_with [`RefCell::map_split`]: https://doc.rust-lang.org/stable/std/cell/struct.RefCell.html#method.map_split [`ptr::hash`]: https://doc.rust-lang.org/stable/std/ptr/fn.hash.html [`Range::contains`]: https://doc.rust-lang.org/std/ops/struct.Range.html#method.contains [`RangeFrom::contains`]: https://doc.rust-lang.org/std/ops/struct.RangeFrom.html#method.contains [`RangeTo::contains`]: https://doc.rust-lang.org/std/ops/struct.RangeTo.html#method.contains [`RangeInclusive::contains`]: https://doc.rust-lang.org/std/ops/struct.RangeInclusive.html#method.contains [`RangeToInclusive::contains`]: https://doc.rust-lang.org/std/ops/struct.RangeToInclusive.html#method.contains [`Option::copied`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.copied

Rust 1.35 changed the behavior of the Debug trait to include the trailing comma in structs and other things. This deals with that by not including all of the whitespace. The Rust change that introduced this was rust-lang/rust#59076 Fixes petgraph#255.

Rust 1.35 changed the behavior of the Debug trait to include the trailing comma in structs and other things. This deals with that by not including all of the whitespace. The Rust change that introduced this was rust-lang/rust#59076 Fixes #255.

dtolnay added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Mar 10, 2019

rust-highfive assigned kennytm Mar 10, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 10, 2019

dtolnay force-pushed the comma branch from 01bb530 to ddcfe2b Compare March 10, 2019 22:45

rustbot added the relnotes Marks issues that should be documented in the release notes of the next release. label Mar 11, 2019

rust-highfive assigned Amanieu and unassigned kennytm Mar 11, 2019

Centril added this to the 1.35 milestone Mar 18, 2019

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 19, 2019

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Mar 19, 2019

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dtolnay force-pushed the comma branch from ddcfe2b to c0d68d2 Compare April 3, 2019 14:32

bors added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Apr 3, 2019

dtolnay mentioned this pull request Apr 3, 2019

Accept trailing comma in test of impl Debug for PackageId rust-lang/cargo#6818

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dtolnay mentioned this pull request Apr 3, 2019

Update cargo #59681

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dtolnay force-pushed the comma branch from c0d68d2 to cfd31fb Compare April 5, 2019 13:46

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 5, 2019

bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 5, 2019

bors merged commit cfd31fb into rust-lang:master Apr 5, 2019

dtolnay deleted the comma branch April 5, 2019 17:54

eddyb mentioned this pull request Apr 6, 2019

Tests are broken on nightly because of trailing commas. rust-lang/gll#88

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teskje mentioned this pull request Apr 28, 2019

Replace all uses of try! with ? lalrpop/lalrpop#454

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teskje mentioned this pull request Apr 28, 2019

Ignore trailing commas in ExpectedDebug lalrpop/lalrpop#455

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waywardmonkeys mentioned this pull request Aug 11, 2019

tests: Fix dot test by not including whitespace. petgraph/petgraph#260

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bjorn3 mentioned this pull request Apr 29, 2020

add support for deserializing and printing std::backtrace::Backtrace athre0z/color-backtrace#35

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Include trailing comma in multiline Debug representation #59076

Include trailing comma in multiline Debug representation #59076

dtolnay commented Mar 10, 2019

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Include trailing comma in multiline Debug representation #59076

Include trailing comma in multiline Debug representation #59076

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